What Happens to Teeth in Space?

By Genni Burkhart, Editor

Humans have lived continuously aboard the International Space Station for nearly 25 years. During that time, astronauts have learned to adapt to an environment that challenges nearly every system in the human body. Preparing for those missions takes years, and almost nothing is left to chance, not even their teeth. In fact, every astronaut receives a dental readiness classification before launch.

While this may seem like just another rigorous medical requirement, the oral health of the astronauts takes on an entirely different level of importance once they enter orbit. Crowns can loosen, teeth can fracture, and pain can begin without warning. However, once a mission is underway, there isn't a dentist, oral surgeon, or a pharmacy to help intervene.

Fortunately, scientists have long prepared for worst-case scenarios like this. Dental research ranges from preflight treatment planning and emergency dental kits to the long-term effects of microgravity on oral health. In fact, it begins months before launch, when astronauts undergo some of the most comprehensive dental evaluations any patient is likely to experience.

Preparing for Launch

The entire process begins at least six months before launch. According to NASA's aerospace dentistry presentation, astronauts receive a complete oral examination at L-6 months, complete any necessary dental treatment by L-3 months, and enter crew quarantine 14 days before launch. By then, their dental work is complete.

NASA's dental readiness standards are designed to identify conditions that could worsen significantly once a mission is underway. A restoration with questionable margins, recurrent decay, or a third molar with a history of inflammation may never become an emergency on Earth. However, everything deserves a second look when there isn't a dentist available, much less a planet underfoot.

NASA also designed a unique dental emergency kit for spaceflight. As you can imagine, it looks very different from one you'd find at an earthly practice. Every item has to justify the weight it adds to the spacecraft and the space it occupies, so only the essentials make the trip.

NASA's spaceflight dental kit includes:

• Temporary filling material.
• Basic dental instruments.
• Local anesthetic.
• Medications.
• Dental floss.
• Temporary cement.
• Elevators.
• Extraction forceps.

Additional supplies designed to stabilize a dental emergency until the crew can safely return to Earth are also included in the kit. It comes as no surprise, however, that NASA places far greater emphasis on preventing dental emergencies before launch than treating them after liftoff. Addressing a questionable restoration, treating recurrent decay, or removing a problematic third molar on Earth is far simpler than managing the same problem hundreds of miles overhead with limited equipment and no dentist for follow-up care.

Life Without Gravity: Can Teeth Really Explode?

Back here on Earth, most dentists aren't thinking about gravity while they work. Water stays where it belongs, suction removes debris, and instruments stay exactly where they're placed. However, none of those assumptions hold true in microgravity.

During the Mercury and Gemini programs, researchers flew a non-vital human tooth on three separate missions to observe how dental tissues responded to spaceflight. A few years later, Lt. Col. Jack Hartley developed a dental kit for missions lasting 30 days or longer. The kit measured just 6 by 12 inches, weighed 1½ pounds, and still included universal forceps, interchangeable hand instruments, local anesthetic, antibiotics, sedative filling material, and exodontia sponges.

Even toothpaste had to be reconsidered.

Dr. Ira L. Shannon developed a foamless ingestible dentifrice called Nasadent, allowing astronauts to brush their teeth without needing to spit into a sink. NASA's presentation even includes one astronaut's review that, "It tastes better than the space food!"

Microgravity oral health studies have found interesting results, including reduced salivary flow, increasing the risk of dry mouth and salivary stone formation. Researchers also documented increases in cariogenic bacteria, including Streptococcus mutans, along with denser dental biofilms under simulated microgravity.

Perhaps a more shocking dental occurrence in space is the phenomenon known as odontocrexis, sometimes called "tooth explosion." Pressure changes can expand gas trapped beneath a defective restoration or recurrent decay, potentially dislodging a filling or crown. Although it's uncommon, the possibility of odontocrexis reinforces why NASA places such a strong emphasis on identifying and treating questionable restorations before launch.

NASA's emergency dental training is built around that same philosophy. Astronauts and crew medical officers train to stabilize problems until definitive treatment becomes possible, including:

• Administering local anesthetic.
• Placing temporary fillings.
• Managing pulpal exposures.
• Temporarily recementing crowns.
• Prescribing antibiotics.
• Performing extractions when necessary.

NASA has documented two caries incidents aboard space station Mir, both treated with temporary filling material and followed by no further complications. The agency also reports a crown dislodged during a Soyuz launch and a temporary crown lost during another space shuttle mission, both of which were managed successfully until they returned to Earth.

Back on Earth

Spaceflight has raised questions that reach well beyond the space program. Military deployments, submarines, Antarctic research stations, disaster response, and remote communities all face the same challenge as astronauts: dental emergencies often must be managed long before definitive treatment is available.

One six-month mission aboard the Mir space station provided researchers with an unexpected opportunity to study a dental implant in microgravity. Follow-up radiographs of a French astronaut showed that the implant remained stable throughout the mission, suggesting that osseointegration held up remarkably well despite prolonged exposure to space. This is an excellent example of managing dental emergencies in the most challenging environments by stabilizing the patient and safeguarding both their safety and the mission's success.

Spaceflight has also prompted a closer look at restorative materials. If a crown or restoration has to survive launch, landing, and months in orbit, the materials holding it in place matter just as much as the restoration itself. Under simulated pressure cycling, resin cement maintained retention and showed no evidence of microleakage, while zinc phosphate and glass ionomer cements lost retention and demonstrated greater microleakage. Although the research was designed for space missions, the findings have helped strengthen our understanding of restorative materials used in everyday dentistry.

After nearly 25 years of continuous human life aboard the International Space Station, one lesson has remained consistent. Whether the patient is sitting in a dental chair or floating hundreds of miles above Earth, the best dental emergency is still the one that never happens.

Author: With over 16 years as a published journalist, editor, and writer, Genni Burkhart's career has spanned politics, healthcare, law, business finance, technology, and news. She resides in Northern Colorado, where she works as the editor-in-chief of the Incisor at DOCS Education.

References

1. Hodapp, R. M., & Haas, A. N. (2022, October 15). Beyond Earth Orbit: Space Dentistry—Challenges, Considerations, and Practice [Presentation]. NASA Technical Reports Server. https://ntrs.nasa.gov/api/citations/20220015316/downloads/2022_SMILECON_Hodapp_Haas_Beyond_Earth_Orbit_Oct%2015.pdf
2. Miller, G. J., Blue, R. S., Johnston, S. L., & Antonsen, E. L. (2022). Medical Capability and Integrated Medical System for the Orion Spacecraft [Presentation]. NASA Technical Reports Server. https://ntrs.nasa.gov/api/citations/20220006714/downloads/MPCV-AsMA-2022-Orion_Spacecraft_Medical_Kit.pptx.pdf
3. Hasin Abdul Samathu, J., Mani, R., Venkatesh, V., Vaishnavi, A., & Sacrapani, L. (2024). Smile Beyond the Stars: A Narrative Review Exploring the Challenges for Dentistry in Space. Cureus, 16(8), e66591. https://doi.org/10.7759/cureus.66591
4. Lyons, K. M., Rodda, J. C., & Hood, J. A. A. (1997). The effect of environmental pressure changes during diving on the retentive strength of different luting agents for full cast crowns. Journal of Prosthetic Dentistry, 78(5), 522–527. https://doi.org/10.1016/S0022-3913(97)70070-2